[BrianG]

Gotta be careful though. High efficiency doesn't necessarily mean hi-quality. Too-high numbers generally means poor suspension control which produces loose muddy bass.

I wouldn't quibble about sensitivity numbers, just make sure whatever driver you choose is in the proper size box. Proper box is the key! I personally prefer ported when done right; has more output at lower frequencies but response drops off fast (24db/oct) for tones lower than the port frequency. Subsonic eq is recommended. I've heard what people think of as crappy drivers sound very good. I've always pushed much more power than a sub is rated (usually around double) as long as it is clean (no clipping) and not listening to something like 20Hz tones all day.